                    [:m :ft]                   #(* % (factors [:m :ft]))
                    [:kg :lb]                  #(* % (factors [:kg :lb]))
                    [:lb :kg]                  #(/ % (factors [:kg :lb]))
-                   [:lb-per-gal :kg-per-m3]   #(* % (factors [:lb-per-gal :kg-per-m3]))
-                   [:kg-per-m3 :lb-per-gal]   #(/ % (factors [:lb-per-gal :kg-per-m3]))
                    [:m3-per-min :bpm]         #(* % (factors [:m3 :bbl]))
                    [:bpm :m3-per-min]         #(/ % (factors [:bbl :m3]))
                    [:F :C]                    #(/ (- % 32) 1.8)

                   [:ft-lb :J]                1.35582
                   [:m :ft]                   3.28084
                   [:kg :lb]                  2.20462262185
                   [:lb-per-gal :kg-per-m3]   119.826
                   ;; slurry rate conversion not needed (use [:bbl :m3])
                   [:m3 :bbl]                 6.28981077}
        converter {[:lb-per-cu-ft :kg-per-m3] #(* % (factors [:lb-per-cu-ft :kg-per-m3]))

        measurement (generate-measurement-f unit)]
    [measurement (measurement-as-f measurement (first (remove (partial = unit) units)))]))

(generate-pair #{:lb-per-gal :kg-per-m3}
               rand-proppant-concentration-unit
               typical-proppant-concentration
               proppant-concentration-as)
